Tech Talk #15 – False Engine Economy

By David Reher, Reher-Morrison Racing Engines

Recycling is unquestionably good for the health of planet Earth, but it is risky when you are building a race engine. My environmentally conscious teenage daughter has impressed on me the importance of recycling soft drink cans and newspapers for the good of future generations. The motivation to reuse race engine parts is usually financial, not ecological. I think it’s just bad business to reuse engine parts that are mismatched, outdated, or just plain worn out in the hope of saving a few dollars. Usually it turns out to be more expensive in the long run, and the results are seldom what you expected.

It is false economy to save a dollar today and end up spending three dollars tomorrow. Yet that is what often happens when a racer tears down a perfectly good engine to change the entire combination. You are generally better off in the long run to build a new engine from scratch than to attempt to turn an old engine into something it was never intended to be.

Suppose that you have a 468ci big-block in your heads-up dragster. You’re having a tough time making the Quick 16 show at your local track, so you logically conclude that you need more displacement. You might be tempted to rebuild the motor with a long-stroke crank and a pair of bigger cylinder heads – but what you are likely to end up with is an unhappy and potentially unreliable engine combination. You’ll also have a pile of expensive used parts – crankshaft, rods, pistons, and heads – that have almost no market value.

My advice is to keep your existing engine in one piece. You can use it as a spare, or sell it as a complete engine to finance your next motor. Even if your old engine isn’t powerful enough to make the Quick 16 show, it’s still more valuable as a back-up or a bracket racing engine than it is as a stack of parts on the floor of your garage.

You are asking for trouble if you bolt expensive new parts onto a tired engine assembly. Your investment in a pair of the latest, trickest cylinder heads can be wiped out in an instant if an old timing chain fails or an overstressed rod bolt breaks. Engine parts have a finite life, so you are gambling against long odds when you bet that you can squeeze another race or another season out of parts that really should be retired.

Even if a recycled race engine doesn’t break, it is unlikely to perform to your expectations. I’ve harped on the importance of having a compatible combination of parts in previous columns, and I’ll climb back on my soap box again. We have built literally thousands of engines at Reher-Morrison Racing Engines, so I understand how heads, cams, manifolds, carburetors and all the rest interact with each other. It is wishful thinking to bolt a pair of 400cc heads onto a short-block that really needs 300cc intake runners. When the engine turns out to be lazy and inconsistent, it may be easy to blame the new heads – but the real problem is the mismatched combination.

It may seem economical to recycle a race engine at the outset, but you will probably end up spending more than you expected. For example, if you buy a set of killer heads with longer valves, you will need new pushrods as well. You’ll want a bigger cam to take advantage of the increased airflow. Of course, the chambers are probably smaller and the valves are larger, so you’ll need new pistons as well. This means new pins, rings, and bearings go onto the shopping list. At this point, you are better off to keep your old engine in one piece and build the engine you really want from the oil pan up.

Perhaps you think that you can’t afford a second engine – but can you afford not to have one? If you go to a race without a spare and something happens to your engine, you’re finished. You’ve lost your entry fee, the expense of getting to the race, the cost of your hotel room, and your time. It’s foolish to save pennies on an engine when you consider how many dollars you spend on your total racing program.

Certainly there are engine parts that can be recycled and reused without jeopardizing your combination. These generally fall under the heading of “Accessories.” Water pumps and starters, for example, are easily interchangeable between the primary and spare engine. There is certainly nothing wrong with swapping a carburetor between motors. When Bruce Allen and I come up with a set of carburetors for our Pro Stock Pontiac that goes down the track, we use them on every engine we run.

My preference is to have a distributor already installed and timed in the spare engine. A distributor is relatively inexpensive, and it’s a hassle to install one when you are under the stress of making an engine change. You should have a spare distributor anyway, so you might as well carry it in the back-up motor.

I come from a frugal family, and I was taught not to spend money wastefully. Thirty years in racing have taught me to always consider the big picture, however. I’ve signed some big checks for dynamometers, CNC machines, race cars, and transporters. I always considered these expenses as investments in our future success. When you are thinking about recycling an engine, my advice is to consider the true long-term costs. You will probably decide that it is better for your bank account to buy or build the motor you really want.